It is known to provide automobile suspension systems with a variety of different suspension system configurations for controlling handling, comfort and performance. For example, it is known to provide vertical struts to counteract vertical deflection from bumps, body roll and the like. In some configurations the strut is attached within the overall steering system whereby the strut also rotates as the vehicle is steered. Such configurations are known as “steerable strut suspensions”.
Stabilizer bars are known in many configurations for vehicle suspension systems and may be connected to the suspension system in various ways. When connected to the strut to act directly against the strut the system is commonly referred to as a “direct acting” suspension system in that the stabilizer bar acts directly on the strut. When a direct acting stabilizer is provided on a steerable strut the connection is somewhat complicated in that the end link used to connect the stabilizer bar to the strut must withstand and accommodate not only vertical movement of the strut, but also rotational movement of the strut when the vehicle is steered right or left, in addition to the twisting moment provided on the stabilizer bar during operation. The link may experience significantly different articulation at opposite ends thereof, with the strut end connection experiencing primarily rotation, and the stabilizer end connection experiencing primarily angulation. Ball joint links have been used in such configurations to accommodate the multidirectional articulations and forces acting on the connections.
A ball joint link includes a rotatable ball held in an attachment which accommodates rotational movement of the connecting end, normally at right angles to the link stud itself. Ball joint links require lubrication, which is held in place by ball joint boots. The boot, which is required for sealing, retains grease in the ball joint structure. However, boots are sometimes easily worn, cut or cracked, and can allow the ingress of contaminants and thereafter trap the contaminants when present in the joint. Ball joint link boots have proven to be components of frequent and regular service or repair. Further, due to the rotational nature of the end of a ball joint link, assembly and installation have been difficult in that the fastened end must be driven into place, and rotation of the end makes it difficult to hold in proper position. Further, ball joint links have been susceptible to corrosion due to wear, and when worn or corroded tend to fail or operate poorly, resulting in noise or other problems.
Conventional grommet end links are also known for use in linear attachments, such as between a stabilizer bar and a control arm. Such end links can be simple in nature with linear threaded components at either end. However, simple linear end links can not be used in many installations of direct acting suspensions on steerable struts due to the rotational movement at the connecting joint.
Accordingly, a grommet end link suitable for direct acting suspension systems having steerable struts has been proposed. The end link includes grommets on opposite sides of a suspension pad and bearing assemblies adjacent each grommet. One side of each bearing assembly is connected to rotate with the grommets and suspension pad, and the other side of each bearing assembly is connected to move with the rod of the end link. Connection via the end link enables the stabilizer system to reduce body roll during vehicle cornering by transmitting force from the stabilizer bar to the suspension. A direct acting end link decouples the rotation experienced at the link during steering while providing a better leverage ratio by connecting to the strut. The improved leverage allows for a smaller diameter bar for reduced mass while providing similar body roll reduction. In such a link, it is necessary to maintain adequate lubrication along bearing surfaces and packed within the bearing to prevent or substantially block the ingress of water or other contaminants into the bearing area. This will reduce wear caused by contaminants getting between the contact surfaces of the bearing as the surfaces rotate with respect to each other repeatedly during operation and use. Wear can cause increased torque, stick, slip or noise as the surfaces become rougher. Further, wear can result in the loss of lubrication. This can potentially cause the link to become less effective and increase grommet wear as the bearing no longer rotates as it should. Without proper bearing lubrication, the grommets can be abraded by the suspension pads, increasing wear and reducing durability.
A labyrinth seal can be used to retain grease in the bearing, and will provide minimal drag and therefore low bearing torque in that, when packed with grease, a labyrinth seal has minimal contact surface areas. Bearing torque is considered to be the rotational torque about the central axis of the bearing assembly. In general, drag created from friction at contact areas and additional areas further out on the diameter of the bearing assembly will increase bearing rotational torque. However, a labyrinth seal does not provide a positive contact seal, and contaminants can follow along an ingress path defined by the labyrinth seal from outside the seal to the inner volume of the bearing assembly. The winding path of a labyrinth seal provides only a passive seal even when fully packed with grease. Further, the non-contacting ribs of a labyrinth seal can allow some side to side movement during normal operation in a multi-directional rotating connection as necessary when used in direct acting suspensions systems having steerable struts. Side to side movement of the bearing components is undesirable in that it can lead to increased wear.
A more positive contact seal can be provided through the use of an O-ring compression type seal to establish a physical barrier; however, a compression type seal creates high bearing torque due to the increased drag of the contacting surfaces. An O-ring seal requires pre-compression to seal properly, to account for its own wear and to account for manufacturing part tolerances to ensure a positive contact seal throughout the life of the part. Pre-compression creates drag on the bearing race as a result of the amount of normal force needed to compress the O-ring. The bearing rotational torque increases since the O-ring contacts at a large radius from the axis of rotation of the bearing and also as a result of the drag force created by friction. Increased bearing torque is undesirable in a multi-directional rotational system of a direct acting end link for a steerable strut system.
Accordingly, for more effective operation of a grommet end link for direct acting suspensions systems having steerable struts it is desirable to provide a more positive seal than a labyrinth seal, but a seal having less drag than a compression O-ring seal.